This invention relates to vehicle powertrains.
Vehicle powertrains generally are comprised of a power source connected via a clutch mechanism to a geared transmission controlled manually or by a series of clutches and brakes both of which provide generally three or more distinct drive ratios. Most vehicles still use an internal combustion engine as a power source. Internal combustion engines generally have a narrow band of operating revolutions per minute (r.p.m.) matched to the torque or driving force as a xe2x80x9csweet spotxe2x80x9d giving maximum fuel is efficiency and minimum pollution.
The effect of the stepped transmission is that in each of the gears or steps the engine is at first subject to high torque demand at low revolutions causing lugging where the piston is moving slower than the flame front in the combustion stroke. As the engine r.p.m. increases, it passes through the sweet spot of balanced operation of r.p.m. and torque with the piston moving at the speed of the flame front and expanding air. The engine r.p.m. then exceeds the balance of r.p.m. and torque requirement and enters an over-speed situation until the next gear is engaged and the foregoing is again repeated through the next and subsequent gear shifts.
On the open highway, more efficiency is obtained by having an overdrive gear that once again more closely balances the engine r.p.m. and torque requirement. This is usually a fixed gear ratio and generally near the maximum capacity of the engine for operating on flat or moderately undulating terrain. When an incline is encountered most automatic transmissions require the driver to operate a manual button or automatically kick down to a lower geared ratio in a relatively large step with resultant inefficiencies. If the load encountered is in the mid top gear/overdrive range, the transmission will often repeatedly change up and down at regular relatively rapid cycles with a resultant acceleration and deceleration obvious to both driver and passengers.
In an attempt to run the engine constantly and consistently in the sweet spot of balanced engine r.p.m. with the required torque and piston speed being balanced with the combustion cycle flame front and expanding gases, prior art shows attempts at combining various gear drive systems requiring a variable speed input. Generally friction drive coned pulleys or rollers are used achieving speed variation by sliding the tapered cones relative to each other. The amount of torque being able to be transferred by this means is minimal and the resultant wear has made this option unworkable Vee pulleys and matching expandable V pulleys using a wide xe2x80x9cVxe2x80x9d belt have had limited success in the low horsepower area.
Variable speed transmissions using hydraulic pumps and motors in prior art are designed so that as the r.p.m. of the output increases the quantity of oil flow also increases causing additional friction loss due to increased flow. In an attempt to minimise this loss, higher pressures and lower flows have been used. This causes very poor low speed torque characteristics The resultant loss of efficiency and performance, with energy loss, heat generation and the need for cooling dissipation through additional circuits and coolers has meant that this form of transmission has not been viable for high speed vehicular application and has only been applied to low speed tractors and mobile machines.
The present applicant""s International Patent Application PCT/AU97/00714 discloses a vehicle power transmission and power train capable of being continuously controlled over a predetermined range of operation by means of an outer transmission and an inner differential gear assembly controlled by two rotatable inputs. The inputs from a microprocessor continually monitor all vital inputs and outputs and making continuous real time micro-adjustments to ensure ease and smoothness for driver and passengers, fuel efficiency and pollution reduction. Although a single power source can be used to drive the two inputs, for example through hydraulic drive systems, the International application primarily describes the use of a split engine or two power sources, one power unit continuously running in the sweet spot for maximum fuel and pollution efficiencies, the second power source being used to balance the variable input forces. The disclosure of International Application PCT/AU97/00714 is incorporated herein by cross reference and are hereinafter referred to as xe2x80x9cthe applicant""s previous applicationxe2x80x9d
For volume automotive manufacture and to minimise capital tooling costs, it is advantageous to use existing high volume engine manufacture. It is also desirable to gain the advantage of continuously running an entire singular power source at maximum balanced r.p.m. and torque, constantly in the sweet spot for maximum fuel efficiency and minimal pollution, and to maintain that operation precisely in all spectrums of vehicle driving range.
It is an object of one aspect of this invention to provide a power dividing device to provide two rotating outputs having variable relative speed of rotation from as single rotatable input. It is an object of another aspect of the present invention to provide a vehicle powertrain and a power transmission capable of being continuously controlled over a predetermined range of operation.
In a first aspect this invention provides a power dividing device to provide two rotating outputs having variable relative speed of rotation from a single rotatable input, said device including a first rotational element driven in rotation about a rotational axis and having a first rotational output; a second rotational element rotatable about said rotational axis and having a second rotational output: a first fluid chamber associated with said first rotational element; first regulating means to vary the volume of said first chamber in response to rotation of said first rotational element: a second fluid chamber associated with said second rotational element second regulating means to vary the volume of said second chamber in response to rotation of said second rotational element; commutator means to at least regularly establish a closed fluid flow communication between said first and second chambers during rotation of said first and second rotational elements; the relative timing of variation of the volumes of said first and second chambers determining the speed of rotation of said second rotational element in response to rotation of said first rotational element.
In another aspect this invention provides a power transmission unit including a power dividing device, an outer main transmission and an inner differential gear assembly;
the power dividing device providing two rotating outputs having variable relative speed of rotation, said device including a first rotational element driven in rotation about a rotational axis by a power unit and having a first rotational output; a second rotational element rotatable about said rotational axis and having a second rotational output; a first fluid chamber associated with said first rotational element; first regulating means to vary the volume of said first chamber in response to rotation of said first rotational element: a second fluid chamber associated with said second rotational element; second regulating means to vary the volume of said second chamber in response to rotation of said second rotational element; commutator means to at least regularly establish a closed fluid flow communication between said first and second chambers during rotation of said first and second rotational elements; the relative timing of variation of the volumes of said first and second chambers determining the speed of rotation of said second rotational element in response to rotation of said first rotational element;
the main transmission having two rotatable input means each respectively driven by the first rotational output and the second rotatable output of said power dividing device, the two input means being operably connected to rotatable output means so that the rotational speed of the output means can vary in proportion to the algebraic mean of the speeds of rotation of the two input means;
the differential gear assembly being arranged internally of the main transmission and having rotatable input means operably connected to two differentially rotatable output means, wherein the output means of the main transmission and the input means of the differential gear assembly are operably connected.
In another aspect this invention provides a vehicle powertrain capable of being continuously controlled over a predetermined range of operation including:
a single power unit;
a power transmission unit including a power dividing device, an outer main transmission and an inner differential gear assembly;
the power dividing device providing two rotating outputs having variable relative speed of rotation, said device including a first rotational element driven in rotation about a rotational axis by said power unit and having a first rotational output; a second rotational element rotatable about said rotational axis and having a second rotational output; a first fluid chamber associated with said first rotational element; first regulating means to vary the volume of said first chamber in response to rotation of said first rotational element; a second fluid chamber associated with said second rotational element; second regulating means to vary the volume of said second chamber in response to rotation of said second rotational element; commutator means to at least regularly establish a closed fluid flow communication between said first and second chambers during rotation of said first and second rotational elements; the relative timing of variation of the volumes of said first and second chambers determining the speed of rotation of said second rotational element in response to rotation of said first rotational element;
the main transmission having two rotatable input means each respectively driven by the first rotational output and the second rotatable output of said power dividing device, the two input means being operably connected to rotatable output means so that the rotational speed of the output means can vary in proportion to the algebraic mean of the speeds of rotation of the two input means;
the differential gear assembly being arranged internally of the main transmission and having rotatable input means operably connected to two differentially rotatable output means, wherein the output means of the main transmission and the input means of the differential gear assembly are operably connected.
In accordance with the invention a single power unit supplies one drive line of the transmission at a constant speed to the power source r.p.m. and a second drive line from the same power unit which by means of captive volumes or rods of fluid, preferably oil, allows the reactive forces of the transmission to react directly against the power source without loss of energy in balancing the forces.
Preferably, the second drive line mechanically varies the quantities of entrapped oil to allow the variation of the speed of the two input to the transmission causing the rotational speed of the output to vary in accordance with the formula
Vout=2xc3x97Vsecondaryxe2x88x92Vprimary
where Vout is the output speed, Vsecondary is the speed of the secondary input provided by the second rotational output of the power divider and Vprimary is the speed of the primary input provided by the first rotational output of the power divider,
In accordance with the invention the power divider uses a unique method of proportionate control of entrapped oil so that the second rotational output preferably always:
Rotates in the same direction as the first rotational output;
Never rotates less than one third of the speed of the first rotational output when the transmission output is in reverse except when used in machines requiring equal speed in forward and reverse in which case the second rotational output can be reduced to zero rpm;
Runs at half of the speed of the first rotational output when in neutral dynamic lock;
Runs at the same speed as the first rotational output when in full forward motion.
The differential gear assembly is arranged internally of the main transmission and has rotatable input means operably connected to two differential rotatable output means, wherein the output means of the main transmission and the input means of the differential gear assembly are operably connected.
Control means are provided and include means for receiving command input and means for determining performance parameters associated with the operation of the powertrain. The performance parameters include the load on the power unit the pressure of the encapsulated rods of oil in the secondary drive line restraining the outer transmission forces, the rotational speeds of the first primary drive line and the secondary drive line of the main transmission, the load on each of the two output means of the differential gear assembly, and the rotational speeds of each of the two output means of the differential gear assembly.
The control means provides closed loop feedback control to continuously monitor, analyse and adjust the performance parameters in response to command input.
The power unit can be comprised of any range of conventional internal combustion engine typexe2x80x94including the Otto engine, the diesel engine, a rotary engine including true balanced rotary engine with compression and expansion cycle or a gas turbine engine as well as conventional electric motor types. The Otto and diesel internal combustion engines are preferred because they represent established mass produced technologies with relatively low production costs.
Preferably, the rotational power output means of the primary and secondary drive lines rotate in the same direction with respect to the power transmission unit.
Preferably at least one of the rotational power output means of the two power drive lines is selectively operably connected to input means of the main transmission of the power transmission unit by clutch means Alternatively the microprocessor sensing at rest zero inputs will output commands to so position the control mechanism for the encapsulated rods of oil to determine the secondary drive line rotational speed to be half that of the primary drive input into the transmission thus 2:1 input ratio will produce a zero output rotation with dynamic lock in zero output position.
The operable connection may also include gear, chain, belt, electric hydraulic or direct engine drive shaft connection means.
The power units, primary and secondary drive, outer transmission and internal differential may conveniently be surrounded by a common housing or be conveniently detachable as an assembly from the power unit.
The powertrain of this invention permits the power unit configuration to be optimised for different applications. For example a constant speed electric motor with provision to be used as a generator for regenerative braking and deceleration. A power unit of any type running at constant maximum efficiency either directly or via a high-speed flywheel encased in a vacuum running on low friction or magnetic bearings used to supply highly variable power demands and regenerative braking such as city driving to provide an extremely low pollution hybrid.
The main transmission of the power transmission unit advantageously comprises a gear train. Preferably, the two inputs means of the main transmission comprises a first bevel gear and an epicyclic gear assembly coaxially arranged to rotate about a first axis. Advantageously, the epicyclic gear assembly comprises an annular pinion carrier that rotatably supports internally arranged epicyclic bevel pinion, gears having axes perpendicular to the first axis. Conveniently, the first bevel gear and the annular pinion carrier are each individually operably connectable to rotational power sources, such as the primary and secondary drive lines from a singular power source or a combination hybrid power source with a singular output shaft providing power to the transmission unit via both the primary and secondary drive lines. Preferably, the output means of the main transmission comprises a second bevel gear arranged coaxially with both the first bevel gear and the epicyclic gear assembly to rotate about the first axis. Advantageously, the epicyclic gear assembly is arranged between the first and second bevel gears with the epicyclic bevel pinion gears in mesh with both the first and second bevel gears. The main transmission, as described, comprises a continuously variable transmission wherein the speed of the output means varies according to the speeds of the input means in accordance to the following formula:
Vout=2xc3x97Vsecondaryxe2x88x92Vprimary,
where Vout is the output speed, Vsecondary is the speed ofthe secondary input (the epicyclic gear assembly) and Vprimary is the speed of the primary input.
Preferably, the input means of the differential gear assembly of the power transmission. unit comprises differential bevel pinion gears arranged radially inside the main transmission to rotate about axes perpendicular to the first axis. Advantageously the output means of the differential gear assembly comprises two differential bevel side gears coaxially arranged in mesh with the differential pinion gears to rotate about the first axis.
Preferably, the first and second bevel gears of the main trarismission each have a centrally formed and axially extending hole, Preferably, the two differential side gears of the differential gear assembly are centrally mounted on opposed ends of two coaxially aligned power output members such as half axles, that extend axially outwards through the holes in the first and second bevel gears of the main transmission and are advantageously operably connectable to drive wheels.
Advantageously, the main transmission is operably connected to the differential gear assembly by a differential frame that is connected to the second bevel gear of the main transmission and which carries the differential pinion gears of the differential gear assembly, The differential gear assembly, as described, has the functionality of a conventional automotive differential gear. This configuration is particularly advantageous for use with primary and secondary power unit and/or drive lines such as hollow shafted xe2x80x9cpancakexe2x80x9d type true rotary engines or turbines or hollow shafted primary and secondary drive lines comprised of gears, sprockets or axial and radial so piston, hydraulic restraining and power supply means to control the reactive energy between the common power unit and the primary and secondary drive line from the singular or hybrid power supply source,
The drive lines can be conveniently arranged on either side of the transmission with the outputs exiting through the respective primary and secondary drive lines to provide an extremely simple, compact and lightweight power train.
Where the powers unit comprises Otto engines or diesel engines, the power transmission unit is conveniently located centrally, beneath or on the same side of the power unit and the primary and secondary drive line which input via hollow gears, sprockets or radial or axial hydraulics with hollow centres as described.
In the case of trans axle front wheel drive application the power transmission unit is conveniently located in relation to the power unit and drive lines to locate between the front wheel assemblies so as to conform with the required lo cation and space to suit current mass produced vehicles.
In the case of a four wheel drive car, tractor or truck, the power transmission unit is conveniently located in relation to the in-line power unit and drive lines positioned to locate the power transmission with the outputs through the respective primary and secondary drive lines and through the axially extending hole of the first and second bevel gears of the main transmission, thus allowing aligned power output members such as half axles to extend forward and aft of the differential gear assembly which in turn provides rotational power by way of universals and torque tubes forward and aft to the front and rear differentials and axles to all four wheels.
In the case of a two wheel drive tractor or a rear wheel drive truck, the power unit can remain longitudinally positioned in the normal traditional manner and the primary and secondary drive lines supply power directly to the power transmission located in the normal position of the standard differential. By this means heavy-duty high torque trucks and tractors which, normally require 10 and 12 speed gearboxes to optimise engine r.p.m. and torque under heavy load and torque demands across a wide spectrum of operating conditions can have the gearbox eliminated by simply adding an additional crown wheel and pinion to the standard crown wheel and pinion, with the provision of the pinions being able to freely rotate within an annular support of the outer transmission members. This provides a stepless speed range from reverse through to overdrive by means of simply varying the ratio between the primary and secondary drive line.
Where the power unit comprises rotary, true rotary, gas turbine or electric engine, the power transmission unit may conveniently be mounted centrally between the power unit on one side as the primary drive line transmission input and the secondary drive line as described on the opposite side, with the power output members extending through the centre of hollow rotor or turbine shafts and through the hollow secondary drive system an the opposite side of the transmission unit. Further, the housing of the power transmission unit may be integral with the common casing of the power units and secondary drive line.
Advantageously, an internal combustion engine can supply a primary direct drive line and a secondary variable speed drive line from a common shaft that constitutes two variable speed drive lines.
The advantage of this arrangement is that a standard high volume mass produced engine can be used as the singular power source or in some applications a flywheel arrangement can be provided as a means of storing kinetic energy. The flywheel may or may not be associated with the power unit. The flywheel arrangement can be used to supplement power input in times of peak demand and/or provide for regenerative braking. The flywheel may be used as directly driven by the singular power source or by regenerative braking by a fixed gearing and overrun sprag clutch between the engine and flywheel, with the flywheel then providing power via a common output shaft to the primary and secondary drive lines. Alternatively the flywheel can be positioned as a highspeed geared position in the primary or secondary drive line with suitable gearing down to the transmission unit primary or secondary drive input.
The power transmission unit descried above conveniently integrally combines the functionality of the main transmission and the differential gear assembly such that input rotational power may be differentially transmitted to two rotational power outputs at continuously variable output speeds while the singular power source runs at a speed and torque giving maximum fuel, efficiency, minimum pollution and smooth vehicle performance.
The control means advantageously comprises a microprocessing control unit having an input device for receiving command input, for example from a vehicle driver, and a plurality of input/output interface devices for providing closed loop feedback control of the performance parameters of the vehicle powertrain. The plurality of input/output interface devices advantageously comprising a plurality of high performance sensors for monitoring, analysing and transmitting data on the performance parameters of the power train. Preferably, the performance parameters continuously controlled by the microprocessing control unit further include performance parameters that are specific to the type of power unit including the variable secondary drive line oil pressures and interactive forces and controls comprising the vehicle power train. For example, where the power unit is comprised of one internal combustion piston engine, the performance parameters continuously controlled by the microprocessing control unit may further include performance parameters that are specific to most efficient fuel burn and least pollution such as manifold pressure and/or boost pressure, engine torque, engine r.p.m., fuel air mixture, fuel flow, sprocket timing, valve timing, variable intake manifold geometry, variable compression, variable precombustion chamber compression in the case of indirect fired diesel engine, combustion chamber conditions, compression ratio and exhaust gas chemistry and temperature.
In use, the microprocessing control unit advantageously provides self-diagnostic closed loop feedback control to continuously monitor, analyse and synergistically adjust the performance parameters in response to command inputs from the driver. Specifically, the microprocessing control unit advantageously adaptively responds to command input and/or analysis of data on the performance parameters and continuously controls speed and torque of the power units and the other power unit variables to maintain fuel burn efficiency and minimal pollutant while continuously controlling the final output speed and power of the powertrain to meet operational requirements by synergistically adjusting the performance parameters, including the relative speeds of the power input means and primary drive line and the secondary variable drive line hydraulic pressures and speed and the reactive load sharing between the transmission and the two drive lines and power unit.
Advantageously, the microprocessing control unit is programmable with a performance algorithm so that it continually adjusts the controlled performance parameters in accordance with the algorithm to optimise powertrain performance. For example, the microprocessing control unit may be programmed to optimise powertrain efficiency. In which case in response to command input from the vehicle driver the microprocessing control unit would continuously monitor, analyse and synergistically adjust the performance parameters of each of the two power drive lines from a singular power unit to maintain the efficiency of the power Unit within peak ranges which simultaneously continually monitoring and adjusting the load sharing between the power unit and primary drive line and the hydraulic pressure and allowance of reduction of drive speed of the secondary drive line to reduce in accordance with the reactive load transferred from the transmission by varying the length of entrapped rods of oil to synergistically control the final output speed and power of the transmission to meet operational requirements. As such, overall power unit efficiencies will be achieved over a wide range of different operating conditions.
It will be appreciated that where the power unit is an internal combustion engine type significant improvements in fuel economy and correspondingly significant reductions in exhaust gas emissions will be achieved. It will be further appreciated that in order to optimise the overall power unit efficiencies, the power unit may encompass a rotary engine, true balanced rotary engine with compression and expansion cycle, gas turbine engine, diesel engine, Otto engine, electric motor or a hybrid combination of power unit and energy storage and regenerative braking system, This could, for example, take the form of an internal combustion engine and electrical generator with high energy low weight efficient battery storage and electric motor power unit or an internal combustion engine with combined flywheel regenerative braking power unit internal combustion engine with a generator and combined electric motor/generator flywheel for energy storage and regenerative braking as a power unit. As a further example an advantageous use of the invention with a combination of hybrid power unit technologies can be used such as a fuel cell which converts methanol into hydrogen, the hydrogen can be fed through a proton exchange membrane fuel cell where it is combined with atmospheric oxygen to provide power for an electric motor which in turn powers an electric motor/generator flywheel for stored energy and regenerative braking. This power unit can supply power to the advanced transmission as described providing the means to have a real time interactive precise control of power usage and regeneration for optimum efficiency in which pollution would be eliminated with only the emission of water vapour. Alternatively a fuel cell and regenerative braking could supply energy to efficient energy storage batteries providing electrical power to an electric motor connected either directly or via an energy storage flywheel to the advanced transmission as described. The transmission microprocessor control would instantaneously adjust the external highly variable load demands to an optimum input power draw suited to the power unit to prevent system overload but to give optimum power output performance.
In another advantageous use of the entrapped oil coming under pressure due to the reactive force of the transmission on the secondary drive line, energy storage and regenerative braking energy may be stored by the oil compressing nitrogen in a nitrogen-charged accumulator that will provide energy on short peak demands such as stop/start situations in city driving.
In an internal combustion engine, the ignited fuel air mixture burns in a flame front continuing out to the perimeter of the confines of the cylinder. The expanding gases that are generated push the piston away from the cylinder head, thereby rotating the crankshaft and providing a power stroke. As the piston moves away from the expanding gases, it increases the cylinder volume. The higher the initial cylinder compression ratio the faster the burn rate and corresponding expansion rate and the need for faster piston speed which equates to higher engine r.p.m. With a fixed compression engine, it is desirable to have the piston speed match the rate at which the gases are expanding for optimum cylinder pressure, resulting in best fuel efficiency and lowest pollution levels. It is the intention of preferred embodiments of this invention to utilise the control of variable rods of oil to allow a variation of the proportion of the transmission reactive forces to vary the ratio between the primary and secondary drive from a common power source. By so doing the reactive forces are cancelled out by the initial drive being from a common drive shaft and the primary and secondary drive, line speed variation applied to the outer transmission continuously adjust to allow the input power source to remain at the optimum balance of r.p.m. and torque for maximum efficiency to meet the variable load demands and to coincide with energy levels required to maintain the desired vehicle speed. By having the function of a stepless variable speed constant mesh transmission as described giving the precise vehicle speed required while maintaining the optimum fuel air burn rate, by varying the engine""s r.p.m. and by varying the compression ratios and fuel air ratios, optimum operating conditions can be maintained in real time across the full spectrum of vehicle speed and energy requirements, giving minimum pollution and maximum fuel efficiency. A further control of the speed of the flame front, particularly related to a diesel engine, is to have a variable displacement pre-combustion chamber and/or the main combustion chamber. The interaction of inputs and outputs from the microprocessing unit allows optimum settings of engine speed, combustion chamber compression ratio and/or pre-combustion chamber displacement, to give smooth even fuel air burn speed (flame front), corresponding with the mechanical movement and speed of the restraining members in a piston or rotary engine.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.